Very high frequency electric discharge tube



Aug. 3, 1948., K. s. KNOL ET AL VERY HIGH FREQUENCY ELECTRIC DISCHARGE TUBE Filed April 22, 1946 uun.n

L'QRMEZIS' SWZZZ M01: JFHAMSMQZMUY Will/Y0] W156i 1 N V EN TORS.

ATTORNEY.

Patented Aug. 3, 1948 VERY HIGH FREQUENCY ELECTRIC DISCHARGE TUBE.

Kornelis Swier Knol and Johannes Marinus van Hofweegen, Eindhoven, Netherlands, assignors, by mesne assignments, to Hartford National Bank and Trust Company, Hartford, Conn, as

trustee Application April 22, 1946, Serial No. 663,838 In the Netherlands December 4, 1942 Section 1, Public Law 690, August s, 1946 Patent-expires December 4, 1962 4 Claims.

This invention relates to an electric discharge tubevfor short and very short waves, for instance smaller than 1 m., and more particularly to the construction of an anode for a tube of this kind, in which the supply conductor for the anode is secured to this electrode about midway between the ends of the latter.

In tubes for short and very short waves the path which the electrons have to cover from the active surface of the anode to this point of attachment is of'importance. (In fact, due to the skin efiect, the electric current passes along the surface of the conductors.) With an anode where this point lies about halfway the ends, this path from the inner surface of the anode to both ends is about equal, 1. e. half the length of the anode. It now appears that when usin such anodes for tubes designed for very short waves, more particularly waves of the order of magnitude of decimetres and centimetres, these distances are too large, so that a limit is put to the use thereof. The present invention enables the operation of tubes at very short wave lengths by means of apertures provided in the surface of a plate-shaped anode of an electric discharge tube, in which anode the supply conductor preferably contacts with it about midway between the ends thereof, the apertures being provided in the vicinity of this point in the anode surface. This improvement may consist of apertures pro vided in the immediate vicinity of the point of attachment, but preferably slits or grooves are provided which extend from the ends towards the middle close to the said point. Thus it is ensured that the distance from the point, where the supply conductor is secured to the anode, to the active surface (1. e. the inner surface) of the anode is very short, and the construction of this electrode has been found suitable for use in tubes for waves of the order of magnitude of decimetres and centimetres.

Since electrons issuing from the cathode are able to emerge through the slits or apertures, which may involve additional damping, a screen or shield is provided, according to a particular embodiment of the present invention, beyond these grooves or slits, which screen or shield covers the apertures and is preferably electrically connected to the anode.

The invention will now be more fully explained by reference to the accompanying drawing in which Figure 1 represents a side view, partly in cross section, of one form of construction of an electric discharge tube according to the invention,

pins i3, #3 lead. Surrounding cathode ii are a grid M to which electrical connection is made by pin I 5 in the top of envelope IE], and an anode I supported in envelope It by means of tube pin 2, which pin also serves to provide electrical connection to anode I. It is understood that pins 2, l2, l3 and is may be supported in the envelope by any means known to the art and may be spaced in any way, the separation of grid, cathode and anode pins as shown in Fig. 1 being preferable for use with very high frequency electric discharge tubes. In Figure 1 the reference number I represents the anode proper, 2 being the supply conductor which is secured to the anode at 3 and is secured in the wall of envelope ll] of the discharge tube according to the invention. In the anode surface are provided slits 4 which extend from the edge inwards close to the point of attachment of the supply conductor. In this way the distance from the point 3 to the inner side of the anode is very small and the electrons need only travel the distance 5.

Figure 2 represents diagrammatically how a slit in the anode can be covered. In this figure the reference number 6 represents the anode proper which is furnished with slits l. The anode itself is provided over a certain length with a rim 8 which merges into parts 9 covering the slits 1 so that electrons cannot emerge through the slits. In this way a very simple construction is obtained, in which the above-mentioned drawbacks are obviated without involving other difi'iculties.

What we claim is:

1. An electric discharge tube particularly adapted for operation at frequencies above 300 megacycles comprising, a cathode, a tubular anode surrounding said cathode, and a supply lead attached to said anode on the surface thereof remote from said cathode, said supply lead being attached to said anode at a point approximately midway between the ends of the anode and said anode being provided with a slit portion extending from opposite ends of the anode to a point adjacent to the point of attachment of said supply lead to said anode, and a shielding member secured to said anode and positioned over and spaced from said slit portion to prevent the passage of electrons from said cathode into space beyond said anode, thereby to shorten the surface conducting path from the supply lead to the surface of said anode.

2. An electric discharge tube particularly adapted for operation at frequencies above 300 megacycles comprising, a cathode, a tubular anode surrounding said cathode, and a supply lead attached to said anode on the surface thereof remote from said cathode, said supply lead,

being attached to said anode at a point approximately midway between the ends of the anode and said anode being provided with slits extending from each end of the anode to points adjacent to the point of attachment of said supply lead to said anode, and a shielding member secured to said anode and positioned over and spaced from said slits to prevent passage of electrons from said cathode into space beyond said anode, thereby to shorten the surface conducting path from the supply lead to the inner surface of said anode.

3. An electric discharge tube particularly adapted for operation at frequencies above 300 meg-acycles comprising, a cathode, a, tubular anode surrounding said cathode, and a supply lead attached to said anode on the surface thereof remote from said cathode, said supply lead being attached to said anode at a point approximately midway between the ends of the anode and said anode being provided with a slit portion free from obstruction extending from opposite ends of the anode to a point adjacent to the point of attachment of said supply lead to said anode, and a shielding member secured to said anode and positioned over and spaced from said slit portion to prevent the passage of electrons from said cathode into space beyond said anode.

4. An electric discharge tube particularly adapted for operation at frequencies above 300 megacycles comprising, a cathode, a tubular anode surrounding said cathode, and a supply lead attached to said anode on the surface thereof remote from said cathode, said anode being provided with a slit extending longitudinally along the anode to a point adjacent to the point of attachment of said supply lead to said anode, a rim arranged on one edge of said slit, and a shielding member secured to said rim and positioned over and spaced from said slit to prevent .passage of electrons from said cathode into space beyond said anode, said supply lead being attached to said anode at a p n pp im te midway between the ends of the anode thereby to shorten the surface conducting path between said lead and the inner surface of said anode.

KO-RNELIS SWlCER. KNOL. JOHANNES MARINUS VAN HOFWEEGEN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,567,260 Garity Dec. 29, 1925 1,672,483 Crowley June 5, 1928 

